For example, in the dental industry, as a die material (so-called dental embedding material) for use in producing a metal (such as gold tooth and silver tooth) to be used for dental treatment, or as an auxiliary material in producing a tooth mold, an artificial tooth, and the like, gypsum-based powder products and phosphate-based powder products are used. These dental powder products are set by being mixed with a liquid such as water at the time of use (at the time of producing embedding material, tooth mold, artificial tooth, and the like). Dust is generated in handling a powder product (hereinafter, referred to as “scattering property of powder”), and therefore products that generate only a small amount of dust (so-called dust-free type) so that a working environment can be kept comfortable are preferred and a large number of such products are distributed.
It is not limited to the dental industry that a working environment becomes good if the generation amount of dust is small in handling a powder product. For example, powder products (hereinafter, also simply referred to as “powders”) are also widely used in various industrial fields such as construction industry (such as building industry and civil engineering industry), various types of manufacturing industry (such as steel industry, chemical/petroleum products industry, transportation machinery industry, and food manufacturing industry). It is often desired that powders used in various industrial fields and powders produced in various industrial fields also have characteristics that dust does not scatter as much as possible.
As one example in the above-described dental industry, Patent Literature 1 discloses invention relating to a low-dust powder dental gypsum composition composed of a four-component formulation containing (a) hemihydrate gypsum, (b) an adjuster, (c) a predetermined humectant, and (d) a predetermined anionic surfactant.
On the other hand, as a method for measuring a scattering property of a powder, a method in which dust is generated by some sort of method, a powder (dust) is collected on a filter from air in which the dust is contained, and the collection amount of the dust is quantified, a method in which a dust concentration in air is obtained from the information on the laser diffraction of sample air, or the like has been conventionally adopted. For example, the aforementioned Patent Literature 1 describes in the examples thereof a method for measuring the mass concentration of dust in such a way that: a predetermined mass of a powder is taken in a metal cylindrical can to be shaken up and down 5 times at 1 up-and-down cycle per second; and the lid is detached immediately after the shaking to measure the mass concentration of dust released from the surface with a digital dust meter at 3 minutes after detaching the lid.